Automatic thermo-electric control.



H. W. LEONARD.

AUTOMATIC THERMO ELECTRIC CONTROL.

APPLICATION FILED JAN. 5, 1906.

Patented Mar. 23, 1909.

4 SHEETS-SHEET 1.

J7EE

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7 $1; Guyana H. W. LEONARD.

AUTOMATIC THERMO ELECTRIC CONTROL. APPLICATION FILED JAN, 5', 1906.

91 5,974. Patented Mar. 23, 1909.

4 SHEETS-SHEET 2.

gwme/ntoz H. W. LEONARD.

AUTOMATIC THERMO ELBGTRIG CONTROL.

APPLIOATlON FILED JAN, 5, 1906.

915,974. Patented Mar. 23, 1909.

iweooeo WW gwvmboz 4 SHEETS-SHEET 3.

H. W. LEONARD. AUTOMAT IG THBRMO ELECTRIC CONTROL. APPLICATION FiLED JAN 5, 1906.

91 5,974. Patented Mar. 23, 1909.

4 SHEETS-SHEET 4.

Nil-

' UNITED PAIEN 1 curios.

AUTOMATIC THERMO-ELECTRIG con'r'noL.

Specification of Letters Patent.

Patented March 23, 1909.

Application filed Janu r 's, 190a. Serial No. 294,691.

To all whom it may concern:

Be'it known that I, HARRY WARnliaoN- AND, a citizen of 'l-ln-i'tcd States, 'l'GSlCllIlg at 'Bronxville, in the county of Westchester and State of New York, have invented certain "new and uselul improvements in Automatic 'lhcrmo-Electric ontrol, of v-hich' the. following is a full, clear, and exact specification.

My invention relates to the production and to the control of heat, and its principal object is to secure a desired control automaticlbmostiorms of my invention the effects of heat are utilized to affect an electric circuit in which an clectro-responsive device is cmployed, and which responds to automatically control, as desired, whatever is to be controlled.

An important application of my invention is to a soldering iron. in ilsiug a soldering iron, the rate at which heat is emitted by it should be widely variable to secure the best results. When the soldering iron is not being used, its temperature should not increase abnormally. On the other hand, when the soldering iron is being used rapidly in soldering, for example, the conductors of an-arma-' lure to the commutator bars in a dynamo electric machine of considerable size, the soldering iron should not become cool.- In order to maintain a soldering iron at a fairly uniform temperature under such widcl var ing conditions of heat withdrawal, it is desirable that the production of heat enerfiy in the soldering iron should be automatica y proportioned to the rate at which heat is to c emitted by the iron to suit the requirements of prac'zticc. By means of my invention, this result is secured, and is particularly applicable to electrically heated soldering irons.

My invention is also very advantageous for use in connection with electrically heated flat irons. In such electric fiat irons as have been before employed, they become too hot when not -in use, and too cool when they are employed to iron damp goods at the highest rates'at' which a workman can work. The large amount of energy required to convert the ater'cdntai-ned in the goodsint'o steam,

' tends to cool the iron and this greatl redness heated the commercial value of an elect'rica V V flatiron'as compared .with the value it would have if its temperature could be maintained approximate} constant, regardless of the character of te goods ironed, their condition as regards dryness, the rate at which the ironis moved over the goods and the pressure applied, a'nd regardless of whether the "iron is in use or idle.

Many attempts have been made to accomlish to some degree these desirable objects, ut so far as I am aware, no one has heretofore successfuly and comn'iercially obtained these results which my invention -'accom-' plishcs.

My invention is susceptible of various modiiieations'as will be. apparent from the following description and accompanying drawings, and the scope of my invcnlion is;

indicated by the appended claims.

Figure 1 is a diagram of apparatus and connections show ing an app'licatlon of my invention; Figs. 2 to 13 are similar diagrams of modifications; Figs. 14 and 15 are sectional views showing the arrangement of the resistance in one form of soldering iron; Fig. 16 is a longitudinal sectional view of another form of soldering iron; Fig. 17 is a section on the line-]7-17 of Fig. .16; and Fig. 18 is-a diagranrihdicating a desirable arrangement of resistances or coils in a flat-iron.

In accordance with m invention as shown in the accompanying (rawings,- 1 place in ood heat conductive relationshi to the heat generating device, such as t o resistance, a device which responds to a change inthe temperature of the heat gcneratin device, and this responsive device is arrange; to affect the current in a circuit which contains clectro-responsive means, which latter accomplishes a change in the heat production. The heat or temperature is thereby automatically re 'ulated.

Referrin to Fig. l a source of energy is indicated at 1 which supplies current to the supply mains 2, 2. At 3 1s indicated a heatingreslstancc connected across the supply wires through a resistance 4-. The latter, resistance me sometimes be variable for the purpose of a justrnent, as ex lai'ned below,

and the'r'esistance 4 is there ore shown as divided into a series of steps and as having ,an adjustable 'arm'5 t o'vary theamount o Adjace'ntto the arm '5,

resistance in circuit.

isa scalefi which ma be graduated to enable the operator to rea ily secure whatever adjust'm'nt he desires. In good thermo-relation to the device heated or to the resistance 3 is laced a wire. 7, havin a' considerable temperature"-coefl'icient, suc as-a wire of nickel or -"1I'Qn. The wire 7 1s connected 40 through the heater 3.

5 vice heated.

by the sired.

across the supply mains 2, electromagnetic windingifia The win is provided with an iron core and a pivoted armature 9. The armature 9 is connected 2 through an 5 in circuit electrically as shown so that when it is attracted by its magnet it will engage the contact 10 and short circuit the resistance 4. A stop 11 is'provided for the armature to limit its downward movement, and

10 this together with the contact 10 is preferably made adjustable, as by means of a screw as indicated. A graduated scale 12 ispreferably arranged in some cases adjacent to the armature for the purpose of indicating 15 to the operator the adjustment secured.

In operation, assuming that the desired adjustment is secured and the armature 9 attracted, the resistance 3 will give out heat until the temperature is raised to a predetermined amount, and as the temperature is increased the resistance of the wire 7 very a preciably increases and gradually diminis es the current flowing through it and the windin 8, until at the maximum limit desired, the current becomes so weak through the winding 8, that it releases its armature 9 which then falls to the position shown. in Fig. 1. This will insert resistance 4 in series with the heating resistance wire 3, and thereby cut down the current passing through the wire 3 so that its heating efi'ect is dimimshed. When the heat of the parts is reduced to a certain limit, the resistance of the wire 7 decreases so much that the increased current which then flows is suflicient to cause the magnet 'of coil 8 to attract its armature 9. The engagement of this armature with the 'contact 10 short circuits the resistance 4, which causes an increased current to flow The temperature will conse uently again rise to such an amount that t e current through the wire 7 and coil 8 is so reduced that the armature 9 is no lon er retained by its magnet and again falls. T llS 5 will reduce the heating effect of the wire 3 device to e, heated. The heat generatingwire can thei'efore be j'vorked at the maximum temperature commercially allowable with good results, apd at-the same time will v be protected from exceeding such temper- 0 ature! 3 In many instances, it will be desirable to have a certain stahie condition automaticall maintained, and yet have means controll'ab e operator to vary the conditlons as deor example, 1t may be desirable to 'cases however, it may I use one constant temperature on a Hat iron when working on one .kind of goods, and a (lifi'erent constant" temperature when workin on another kind of goods. Adjustment wil also be desirable in connectlon with may be accomplished by varying the air-gap on the magnet. For this purpose, I have indicated the stop 11 as ad ustable, as well'as the contact 10, and it will be desirable to mature of the magnet, which scale may be calierator. The operator can thus. adjust t e armature to a position corresponding with a certain desired temperature,which temperature will-be automatically maintained. Another adjustment for this purpose will be to provide the armature 9 with an adjustable weight, such as 13. Likewise, other forms of adjustment may be provided. The revary the mmlmum current which will pass tor, and a calibrated scale 6 may be provided to indicate the minimum amount of heating or parts thereof, are in circuit. In the same way it will be desirable to provide an ad justable resistance, such as 14, in series with the heater 3, and outside of the shunted resistance so that by adjustment of this resistance 14 the maximum current flow through the heater may be varied. A suitable scale 15 may be provided and so calibrated as to indicate the maximum flow of current, and

pated.

It is desirable to make the air gap of the controlling magnet sufficiently large or the magnetic circult be so designated, that the magnetic pull upon the armature with the same amperes is nearly the same when the arthe other limit of its travel, so that a slight change in the current strength will cause the armature to beattracted or released and thus make the apparatus quite sensitive.

In most mstances, 1t is ver advantageous side of the tool, or other object heated, as it is then not subjected to any considerable heat and can be readily ins ected, adjusted, repaired etc., without inte erence with the device controlled. Also this arrangement is desirable, as the controlling device does not occupy space on the tool or other device controlled, and does not unfavorably affect its more rugged and simple. In some special bedesirable to have the a tomatic contro ing device located in immediate proximity to the source of heat, and perhaps contained in the same apparatus It is obvious that instead of using s'istance 4 is preferably adjustable so as to through the heater 3 at the will of the operawhich will be secured when the resistance 4,

to have the automatic contro ling device outweight and size, and the tool may be made other applications of my invention. This place a scale, such as 12, adjacent to the arbrated in degrees for convenience of the o the maximum amount of energy to be dissimature Is at one limit of its travel as when at gravity to oppose the attraction of the controlling magnet upon its armature, as in F 1g. 1, a spring or other pressure may he substituted, and if the controlling means is located in the tool itself, a spring would probably be preferable.

By means of my invention, the current in the heating resistance may be varied extremely, and thus make a heated tool respond quickly and eilicicntly to the changes in the rate at which heat energy is drawn from the tool, and the heating resistance may be subjected for short periods to currents which, were they not automatically reduced by the controller, wouldsoon cause the resistance to be burned out. Thus, while obtaining high temperatures, I avoid .subjccting the resistance to destructively high temperatures and thus reatly prolong 1ts.l1le. With the excessive y high temperatures, which former apparatus acquired when standing idle, the working surface of the tool was likely to be injured and there was also likelill()()(. of bad e'fi'ects upon the work when the tools were put into use. a For example a soldering iron would have its surface oxidized so that the solder would not flow wcllon its surface, and a flat iron would, be likely to which are worked'upon.

coefficient instead of a scorch the goods to which it was applied when overheated, due to standing idle.

One of the greatest advantages which my invention accmnplishcs, is that a workmans outputcan be very greatly increased, since the temperature of the tool will be automatically maintained substantially constant no matter how rapidly the operator may work, and no matter what the character of the goods is As the output and quality of workdonc by the operator is the most important factor in such cases, a great economy results even though the cost of eleetricenergy is comparatively high, and even though iirst cost is greater.

Instead of using a wire 7 of nickel or some similar resistance, it may sometimes be dcsirable to use a material having a negative positive temperature coeflicient. In such a case the arrangement mightbe that shown in Fig. 2, in which the wire 7 is replaced by a material 7 ohm ative temperature coefficient, and in 'whic l the parts 10 and 11 of Fig. 1 are transposed. Thus, when the temperature of the heater or tool rises to the maximum amount, the cur-- sistance 4 to cause the heating effect ct 3 to be increased .h) Fig. 2, l have indicated an additional means for adjusting the action of the automatic controller. This is the insertion of a variable resistance 16 in the circuit of coil 8, and this variable resistance ma be irovided with a calibrated scale 17 whic i will indicate to the operator the effect that will be produced. As this variable resistance wi I determine the current that will flow in the coil 8, its adjustment will determine within certain limits the temperature of the part 7 that will cause the attraction or releascof the armature 9 by its magnet.

It may sometimes be desirable to employ a relay device in connection with the controlling apparatus, as when the watts controlled are too large to be readily carried without the relay device, or where increased sensitiveness is desired. An arran cment of this kind is illustrated in Fi 3. l h this case the circuit controlled by tie movement of armature 9, is that of a solenoid switch 18. When the solenoid switch is closed by the movement of armature 9 to the contact it), the resistance 4 in series with the heat producer3 is short circuited, causing the amount of heat yielded by 3 to be increased. As soon as the temperature is raised as before described, the increased resistance of the wire 7 will cause the armature 9 to. be relcased, which will break the circuit of the exciting coil of switch 18, which latter will then open. This will insert the resistance 4 in series with the heat producer 3, and reduce the heating effect as already explained. in the present figure, l'have shown the ad justable resistance 16 as shunting the coil 8, instead of being in series with it as in Fig. 2. Variation of this shunt resistance around coil 8 will,ol' course, vary the current that will llow in the latter and likewise ail'ord means for adjustment of the apparatus so that it will operate to maintain a desired condition of temperature.

My invention may be useful in some cases to the control of heat which is not derived from a source of electricity. For example, 1 may employ the ten'iperature of a furnace, or of a liquid, solid, or gas to act upon the heat responsive controlling resistance, and there by control the gas flame which may be the source of heat, or I ma control dampers, fans or other means which will control the production of heat as desired at its place of application. Similarly, I may control a refrigerating instead of a heating apparatus, whereby the temperature at some desired location will be automatically maintained within certain limits. Fig. 4 illustrates an instance of application of my invention to the control of this character. This indicates a material 19, which is heated by a gas jet 20, and the supply of gas is controlled by a valve 2]. The valve is controlled by a core 22, the coil-23 of which isconnected in series with ture of the mined amount, the current througi the re' an electrical lamp of temperature and consequent increase of the heat responsive resistance 7. The movement of the valve 21. is limited by the adjustable stops 24, .24. 'When the tem eraoily 19 has reached a are etersistance 7 anrYcoil 23 will be so reduced that the core 22 will fall and turn the valve to de crease the supply of gas. On the other hand, when the temperature becomes lower, the current through the coil 23 and resistance 7 'is increased and the core 22 is raised, and the valve 21 will then be opened to supply a greater amount of gas and heat to t emat'eral 19.

My invention maysomet'imes be employed to give an audible, visual, or other form of current through the coil 8, will cause the armature 9 tobe attracted which will break the circuit of the signal or signals, and show,

that the temperature is below the maximum limit.

It may sometimes be desirable to en i ploy two or more controlling magnets, eacg controlling a set of resistance so as" to ecure greater refinement of automatic con pol of the heat generated, and to secure othe ad- A magnets is shown .in Fig.

vantages which may arise from the employ:

ment of severalsteps as com ared with one step. An arrangement in w ichtwo steps of resistance are used with two controlling 6. In addition to the parts shown in Fig. 1, a second set of controlling means is shown, having corresponding numerals to designate the same parts, except that the numerals. of the ,additional set are rimed. The resistances- 16, 16 form variable resistance shunts around .the coils 8, 8 so that each may be adjusted to cause their armatures to be attracted and released upon the occurrence of certain definite currents through the responsive resistance 7. The coil 8 may be adjusted and designed to attract the armature 9 upon the occurrence of a greater current through the resistance 7, than that upon which the coil 8 will attract its armature 9 such a case, if the temperature of the device to be heated drops below a certain amount, the armature 9 will first be attracted and cut out the resistance 4 to increase the heating effect of the heat producer 3. If this proves to be insuflicient to raise the temperature, and a further dro in temperature occurs, the armature 9 will t en be attracted and short circuit the resistance 4, which will cause a further increase in the heat production, Likewise, if the temperature becomes equal 7 rises to a predetermined I to a certain amount, so that the resistance of 7 is increased to a certain degree, the armature 9 will first be-released, and if this does not reduce the heating sufficiently by the insertion of resistance 4, and if the temperature is further increased, the armature 9:

will next be released and the heating effect will be further reduced by the insertion of resistance 4. Similarly, if desired, a greater number of controlling devices may beused.

Instead of using a responsive material of variable resistance upon change of temperature, and thereby control the current in an electro-responsive device, a thermostat or other device may be used, in which a change in temperature causes a mechanical movement. When such movement occurs, an electrical contact will be made or broken to control the current leading to an electro-responsive device which will control the insert1on or cutting out of resistance to affect the heat production. Fig. 7 shows an arrangement of this character, a thermostat 27 being placed in good heat conductive relation to' the heater 3. When the heating has raised amount, the movement of the thermostat .will be such that it moves away from a air of contacts 28, opening the circuit of coi 29 of an electro-magnetic switch 30. The switch 30 is then opened; and the resistance 4 insert'ed in series with the heat producer 3 to, reduce the heating effect. When the device has cooled to a certain temperature, the thermostat will move to engage the contact 28,

closing the circuit through coil 29, and thereby closing the switch 30. This cuts the resistance 4 out of circuit and increases the heating effect as already explained. My invention may also be applied to the protection of armatures of dynamo electricmachines, or other devices which may become unduly heated, so that when the temperature exthe temperature of the device to a certain ceeds a predeterminable maximum, the heat responsive device associated therewith will aiiect a circuit containing an electro-responsive device, which may give an indication or alarm, or put into action a device which will reduce the heat generation. I

In lace of the magnet and 'ivoted armature s own in Fig. 1, a solenoi and core may be used as indicated in' Fig. 8. Here the solenoid coil 31 in circuit with the variable resistance 7 acts to control the position of its core 32, and vconsequently the opening or closing of the switch for short circuiting the resistance 4. Various adjustments ma be applied to the solenoid and sw' ch sue as o f change 1n turns or position of coil 3.1 'osltion of contacts, weight and lower posit'io "of corei and resistance of the circuit containing mi 31 or of a shunt resistance about 0011 31, etc. and these various adjustments ma be applied to man of the constructions ascribed ,erein as wi of course be understood.

' circuits the coil 34,

plainedwill again take place.

switch 43 is closed,

-circuit wit In Fig. 9 is shown an ai'rangement in whi h Yis-usedfbiit which is somewhat different'; from tlie' constructionand connectionsoi' Fig.3. t ln the' present figure, the switch 33 is controlled the coil 31 and ,qgens .or clo'ses'a shuntlcircuit aboutthe coil 34; j The latter'is iii circuit withthe heatingresistance 3. The coil 34 through .its core, controls a swi'tch'35 which includes .or cuts outthe resistance 4 from the circuit of the heating resistance 3." When the apparatus .is connected to the supply wiresa comparatively st1'ong" cu1jrei1t will flow through the resistance 7 and coil 31 and raise core-32, thereby openingswitch 33. This willcause .the current through coil 34 to raise switch 35 and cut the resistance 4 out of the heating circuit. When thetemperature of the. heated parts rises to the maximum, the current in coil 31 willbe so decreased as to cause the core 32 to fall and close switch 33. This action short and the switch 35 will fall and cut resistance 4 incircuit. The heating effect is thus decreased until the temperature is such that the currentiin coil 31 causes its core to be raised, when the action above ex- The temperature is thus regulated within limits.

In Fig; 10,the raismg of core 32 by thecurrent .in its coilopens switch 361whic shunts coil 34 connected across the line through a resistance 37.- The heater 3 is connected across the linethrough a switch 38-control1ed by the coil 34 and its core. Upon connectin to the supply line, the current in coil 31 wi raise its core and open switch 36. This'will cause current to flow through coil 34 and so close switch 38. Current then assesin resistance 3 and the temperature olthe parts is rapidly increased. When switch 36 is afterward closed by reason of the higher temperature attained, the short circuiting of .coil 34 will open switch 38 and the current to the resistance 3 will be interrupted. When the temperature sufficiently decreases, relay switch 36 will be opcnedand switch 38 closed as above explained. v

In Fig. 1], instead of using separate heating and controlling resistances, a single resistance-39 is used of nickel, or iron, or other high tem erature coefficient material. In 7 the resistance 39 is the .resistance 4, which is shunted when switch 40 is closed. This switchis controlled by coil 41 and its core and this coil is incircuit with theentire coil 42, which controls switch 43. When it shunts a part of coil 42 and also shunts coil 41. When the device is connected to a source, current will first flow through coil 42, coil 41 and heater 39. This will be sufiicient to raise the cores of coils 42 V and 41, closi'ngswitch 43 and opening switch 40. The closing circuits coil 41 so that switch 40 will .be closed and a considerable current will pass through above described.

i l I a portion of ;coil..42, switch 43, switch 40 and heating resistance39. Althoughsome turns of coil 42 are cutout at this time, its-core will still beraised on accountof the increased cur rent flow 'and.on .-account of less excitation being required to hold thecore atterbeing raised. Adjustment of the number of turns out out, will givea suitable relationship. As the temperature of the resistance 39 and other art or parts heated rises, the current throug hthe remaining effective turns of coil 42 gradually becomes. less owing to the increase of resistance of 39. The core of coil 42 will finally drop when the maximumtemerature is reached andso open switch 43. so his will causethe current to pass through the remaining turns of coil .42 and also through'coil 41 which will raise its core-and open switch 40. The complete ath .of the current will'then be coil 42, coil 4.1, resistance 4 and resistance 39. The reduced stren th of this current-cuts down the heating efiect of 39, but as the temperature decreases the resistanceof39 becomes less and the current strength gradually rises. When this is sufiicient to raise the core ofcoil .42, the switch 43 will be closed and the increased current will flow through resistance 39 as The temperature is thus closely regulated and without re use of separate heating and centre anccs;

In some cases, to the control of ina s st ,I may app y my i ention an electric current or electromotive force; in such a case the heat responsive resistance will be arranged in a circuit, the current in which is normallyconstant within limits. Chan e in the current strength will then change t e resistance and this change in resistance may then be used either directly or'indirectly to'automatically prevent too wide a change from normal conditions. For example, in Fig. 12 is indicated a generator armature 44 supplying current to the mains 2, 2'. The field 45 is controlled by 1 10 a variable resistance 46; the path of the field circuit being from line 2, through the field circuit 45, resistance 46 and its adjustable arm 47, throu 11 the resistance 48 of nickel or other materia? of considerable temperature to line 2. The resistance 48 is shunted by a magnetic .winding 49. The latter acts to attract or release the armatureswitch 50 in 0E1; positionto spring 51. Themovement oft e armature 50 controls the current to the reversible pilot motor 52, which latter regulates the position of the arm 47.

In operation .the electromotive force sup-v plied to the mains will be maintained substantiallyconstant as followsi Suppose the electromotive force rises somewhat above. the normal value, .then since the resistance 48 of switch '43 however, short is in circuit across the line the. increasedcur and consequent the 9s y force relatively more current throu themagnet winding 49. The

, rent in 48 will be less and as its temperature and vresistance lowers, it will tend to take more current from the winding 49. The force of spring 51 will then be stronger than that of the magnet and ture 50 'to contact 55. The circuit throughthe pilot motor will then be the same except thatits field will be reversed, the field 56 now being excited instead of field 54 and in a reverse sense. The pilot motor will therefore rotate 'to cut out part of resistance 46 and so cause the generator to supply an mcreased electromotive force. A practically constant electromotive force can thus be maintained. 1

In Fig. 13 is shown an arrangement of apparatus for maintaining a constant current in a desired circuit. An instance of a storage battery 57 is shown supplied from the mains 2, 2 and source 1. W 1th the arrangement shown,.a ractically constant rate of charging may e maintained without danger of objectionable effects from too rapid charging. In series with the battery 57 to be charged, is an adjustable resistance 46 controlled by the arm,47. Also in series therewith is the controlling resistance 48 temperature coeflicient material. A magnetic winding 49 is shunted about the resistance 48, as in Fig. 12. The winding attracts or releases its armature switch 50 to engage either contact 53 or 55. If the charging current becomes too large, the increase in resistance of48 causes the winding 49 to attract its armature, and the pilot motor will rotate to insert more of resistance 46 in series with the battery to reduce the current. When, however, the current is too small, the resistance of 48 will be so low that a reduced current will pass through the windin 49 and so release its armature 50, which will engage contact 55. The field 56 of the reversible motor will then be excited and cause the same to rotate in the opposite direction. and so cut out more of resistance 46 to increase the cur-rent fiow. A constant charging current within limits is thus maintained.

When my invention is a )plied to a heatmg device, .it is desirable t at there should .be the best possible flux of heat from the I source of heat to the device heated, and also tothe heat responsive device. Various will draw the arma'-' of high constructions may be employed to secure a high degree of heat conductivity between the heat e'nerating resistance and the heat re sponswe resistance, when that is employed. 1 sometimes-wind the heat generating wire and the heat responsive wire on a common support, and they may be wound together, one over theother, or they, maybe displaced longitudinally with reference to each other. Sometimes, mon metallic sup ort, such as copper.

In Figs. 14 an 15, I have indicated a construction of a soldering iron, in which a tube 58 of metal, porcelain, or other material, is shown having enameled thereon the heat producing and heat res onsive resistances 3, 7. Over the outside of this resistance tube is placed a yieldable material 59 having high eat conductivity, such as cop er-foil, copper gauze ,or' copper wire.

cylindrical parts, 60, 61. These are adapted to be drawn firmly together by the screws or bolts 62 passing through lugs or flanges on the parts 60, 61. There is thus secured an excellent heat conductive relationship behe; whole is seated in a hollow shell formed of two semitween all arts of the soldering iron, so that there will e a quick response of the electroresponsive device upon change in temperature. ances in place should have a high fusing point, and )referably a glazed surface. Instead of splitting the soldering iron as indicated in Figs. 14 and 15, a role could be bored or formed therein and the resistance device with its copper sheathing could be made to form a tight fit in the hole. A threaded engagement of the resistance unit with the inside of the soldering iron might be desirable.

In Figs. 16 and 17, a soldering iron is indicated having four tubes arranged ninety degrees apart, three of which, such as the tubes 63, are resistance units for the heat required, and the fourti tube 46 is a unit embodying the responsive resistance 7. The units are shown as surrounded by a good heat conductive yieldable sheathing 59, and are held firmly against the core 65 of the iron by means of the semi-cylindrical clamps 66. A cylindrical cover 67 of some material having lined with such material may be provided roducing low heat conductivity, or

outside of'the resistances to'protect them from mechanical injury and to confine the heat 'enerated.

In Iig. 18, I have 'indicatedadesirable arwhich may also be in the form of an enameled The I 'rangement of the 'resistances'in a flat iron.

mama.

tubular resistance unit, and is centrally located with reference to the heating resistances 68.

Having thus described my invention, Ideclare that what I claim as new and desire to secure by Letters Patent, is,-

l. The combination of a heat producing solid resistiveconductor, an electric conductor whose resistance is responsive to a change in temperature, and means controlled by said response for regulating the heat produced by said heat producing device.

L. The combination of a heat producing solid resistive conductor, a conductor whose resistance is dependent upon the temperature, and clectro-responsive means dependent upon change in the resistance of said conductor for regulating the heat produced by said heat producing device.

3. The'combination of a heat producing solid resistive conductor, means forincreasing and decreasing the production of heatby said device, a resistive conductor whose resistance varies according'to the temperature of the device heated, and means electrically responsive to said change in resistance for controlling said first named means.

4. The combination of a circuit comprising a solid electric heating resistive element, said circuit having means for'increasing' and decreasing the current therein, a second cir= cult functionally related thereto in which the resistance is. automatically responsive to the condition of said first circuit, and a device responsive to change in current in said second circuit for controlling said means.

5. The combination of a solid heat )roducing conductor, a second conductor w ose resistance is affected by the heat developed insaid first conductor, and means responsive to change of resistance in said: second conductor 1' or varying the amount of current llowm in said first conductor.

6. 'lhe combination of a heat producing device comprising a solid heat producing resistive element, electro-responsive means for controlhng the heat produced by said device and a heat res onsive variable resistance for controlling saic means- 7. The combinatlon of an electrically heated device whose temperature 1s to be controlled, a heat producing device, a controlling electric circuit the resistance of which is responsive to the temperature of said first named device, and an electro-responsive device responsive to a change in said resistance.

8. The combination in an electric heater of a heating. element, a. heat responsive resistance, and electro-responsive means controlled by a change in said resistance for regulating the current insaid heater whereby a desired condition within certain limits is automatically maintained.

9. The combination of a heat generative heated, electrical means for heatin solid electric resistance, a heat responsive.

electric resistance functionally relatei there'- to, and means responsive to change in said second resistance for controlling'the heat generated by'said first resistance to maintain a desired condition of temperature.

10. In an eleotro-heatmg apparatus the combination of a resistance which varies in response to change 'in temperature, and magnetic means responsive to such a varie tion in resistance foraflecting' said temperature.

11. ?Inan electro-heating apparatus the combination of a resistance having a high temperature co-efl'ic'ient, and electro-responsive meanssub'ect to change in resistance for automatical y maintaining a. desired condition within limits. v

12. In an electro-heating-apparatus the combination of a medium. or body whose tem eratu're is to be controlled, and a control mg circuit therefor containing a source of 'electromotive forceand a heat responsive resistance.

13. The combination of a mass from which heatis emitted at varying rates, and resistance-responsive means com )rising a' movable element for automatica supplying to said mass heat energy according'tothe demand.

14. The combination of a mass from which roportional to the rates of heat emission y said device, said means comprising a heat responsive resistance, and a functionally reiatod electro-responsive device.

16. The method of controlling the temper-- ature of a mass or medium which consists in transmitting heat from said mass or medium to a heat responsive electrical mearis, varying a controlling electric current, controlling thereby the movement of an electroresponsive device and thus controlling the supply of heat to said mass or medium.

17. The combination of a. mass to be said mass, and separable material of higi heat conductivity compressed between said mass and said. means. 1

18. In an electro-h'eating apparatus the combination of a heatin circuit, a controlling circuit thcrofor, an a resistance in the to the heat in the heating circuit whereb the heat produced in the heating circuit 1s.

automatically controlled. I

19,-In an electro-heating apparatus the controlling circuit automatically responsive exterior electro-responsive device for con- 'trollm lingl the heat produced comprising a con-' combination of a'device topbe heated," means I for electrically heating sald device, and an the heat developed in said first-,- name develo ed electrically. J

, 20. 11 an electro-heating apparatus the combination of an electric heat producing device and means for automatically controltro ng resistance responsive to the temperature of said device.

'21. The combination of means com rising a'solid conducti electric heating e e ment' for heating a dev1ce,'a heat responsive resistance, and an electro magnetic device controlled by said resistance for controlling said means.

. 22. In an electro-heati apparatus the combination of asource 0 electric energy, heat generating means connected to sald device and responsive to the heat} aheatjresponsive resistance.

23. The method of electrically heating which consists. in generati v passage of a current through source, and; controlling means I comprising conducted thereto, and controlling by the said variation of resistance the rateat which the heat energy is generated.

24 The method of controlling heat which conslsts in varying a heat responsive resistance 'by conducting heat thereto, and controlling the rate of production of the heat by said variation in resistance.

In testimony whereof I 'aflix my signature, in presence of two witnesses,

' H. WARD LEONARD.

W1tnesses: I HENN EDMUNDS,. BYRON'E. ELDRED.

heat by the 2.3 v a resistance, iva'rymg a controlllng resistance by heat 

